Scheepers, who won her maiden WTA title at the same tournament last year, went down 1-6, 5-7 against Polish fourth seed Urszula Radwanska, who progressed to the penultimate round.
The South African women's number one, seeded fifth, had defeated Chinese wild-card entry Wang Qiang and Serbian Bojana Jovanovski in straight-set victories in the first two rounds.
Last season, Scheepers became the first South African woman in eight years to win a WTA title when she beat Slovak Magdalena Rybarikova in straight sets in the Guangzhou final.